Radio repair progress

[DonaldSmith]

Less than two weeks ago, I bought an extra 6 v battery, and set up a bench test of the Mopar 602 from my 47 DeSoto. Since then things have been moving at breakneck speed, compared to progress on other items.

First, I got the schematics and some good advice from nostalgiaair dotcom. I was able to resuscitate the vibrator with 120v AC through a light bulb as a resistor. After reinstalling the vibrator, it was humming and my rectifier tube was glowing. On to capacitor replacement.

Then, I ordered capacitors on the web, from radio daze, for less than $20, and installed them. Oh, the $20 included a spool of dial cord. I got the dial pointer working. (Anyone need 15 ft of dial cord?)

Following some on-line advice, I pulled and replaced the tubes in sequence, listening for a speaker pop, a sign that the tube is good. I found that the rectifier, outlet tube and detector tube seemed to be working, but the next ones didn't. Then I was haunted by the new electrolytic capacitors as they gave up a ghost.

When they say ground the negative side of an electrolytic capacitor, they mean connect it to the chassis, even if the car is positive ground. I did it the other way around, and after a short while the speaker hummed loudly even with the volume turned down, a sign that the filter capacitors are shot.

So, I just ordered $4 worth of new electolytic capacitors, and $10 worth of tubes, for another go-round. I feel optimistic. At this point, the high voltage supply works, the speaker works, and some of the tubes seem to work. (And the dial pointer works.)

For years, I had noted that radio repair was in the $200 range, and it seemed that diagnosing and fixing the radio myself was way beyond my expertise. But in searching the web for a good set of schematics a found a radio forum that lends its expertise for free (sort of like the p15-d24 forum's expertise on almost everything useful to know). So . . .

Capacitors and dial cord - $20.

More capacitors to replace the fried ones - $4.

Tubes - $10.

Solder sucker, connectors, shrink tubing, etc. - $10.

Fixing your own radio - priceless.

[Ed Griffin]

Keep us informed of your progress Donald. I've been following your post's and keeping notes and it has been very helpful, thank you, Ed

[Don Coatney]

While talking to Rodney Bullock yesterday one of the things he said was "If I can visualize something in my mind I can make it happen". Rodney’s Plymouth is proof that his way of doing things works. I would have struggled finishing (or even starting) a project like Rodney’s Plymouth having seen his before and after pictures. I applaud his thought processes and determination to stick with a project to the end. Sounds very much like that is what you are doing Donald. Sort of fits in with my philosophy while doing my car that failure was not an option.

[David Maxwell]

I spent $195 having mine completely refurbished. Bob's Radio did and excellent job and they throw in some extra things like, cleaning, and repainting the area that looks like a zinc coating (they do not repaint the hammertone area). So, I'm happy, but I really would have gotten a lot of satisfaction out of doing it myself and apparently saved around $150. So, GREAT JOB! And thanks for sharing the info!!

[Johnny S]

I've been following along as well. I have a couple 803's in need of a tune up and I think it would be fun to fix them up as well. Thanks for pointing out some of the issues you've faced. I would be interested in knowing the websites that you found of value as well.

[John Mulders]

Job well done Donald.

Think it requires a lot of patience and time to find the right stuff.

For me the radio is still far away, not really need one with the engine humming

John

[DonaldSmith]

Look inside your radio for the manufacturer and model. Mopars were made by different manufacturers. Go to nostalgiaair.org, resources, for schematics by manufacturer. My 602 was a Colonial 671A. They had 3 clear pages of detailed information for my radio from a classic radio repair book by a John F. Ryder.

For help, go to the nostalgiaair forum and post your questions. They told me how to resuscitate my vibrator, and what I did wrong connecting my big capacitors. But some of the guys get carried away, since they are dedicated electronic hobbyists. For the price of some of their recommended test equipment you could buy the capacitors and tubes for several radios.

I copied some diagnostic suggestions from a dcosby, but I haven't found it on his latest website. Basically, he put me onto replacing the paper and electrolytic capacitors and pullling tubes to pop the speaker. If I can't find his article on his web, I could e-mail it to you if you want. judyanddon@sbcglobal.net

I got my capacitors and ordered my tubes from www.radiodaze.com. $10 minimum order, plus actual shipping cost for USPS, in my case less than $5 for a 6 x 6 box (It had to be big enough for a spool of dial cord.) Order filled and picked up Monday, arrived Wednesday.

You can always yahoo or google words like "antique radio", or your topic of the minute. That's how I found all my gems. Some sites sell parts or schematics, but may still post some free information.

Good luck. Have fun.

[Johnny S]

Good stuff....thanks.

[BobT-47P15]

There was some fellow on ebay from California selling complete sets of tubes for the 802 radio. I bought a set, just for insurance, as my radio is not working currently and I don't really care if it does. But, may change my tune some day and want to get it going. Also purchased a new reproduction dial glass sometime back from a man in Canada.

[Norm's Coupe]

Bob, I too bought a set of tubes and a new dial glass on the bay for my 802 radio. Tubes are in the box they came in, sitting on a shelf in the garage. Radio has been removed from the car and is on a shelf in the cellar. The new glass dial is still in the package, on the shelf below the radio. All I need now is some time, and a round tuit.

Sounds like you and BobT are ahead of me. I have not spent a penny on tubes or capacitors, or a new dial for the radio. Actually the dial on mine looks good anyway. However, my radio is also in a cabinet and does not work. I replaced the radio with this dummy head. The head has a place for a bulb so will put that in someday when Shel sends me the round to it when he finds it.

[maurice wade]

Donald, I have a 47 and the radio can be heard, but it also has a LOUD hum that does not go away. What could this be? I got to looking at the wires around the radio and noticed a wire that had a round plastic object the size of maybe a quarter, and about 3/4 inch thick. It looked like it could have been attached to something, what could this be? Any ideas to anyone? Thanks for help, M Wade

[eric wissing]

The hum is most likely a filter capacitor. I am not sure what the other object is that you are talking about is. Eric

[Don Coatney]

Donald, I have a 47 and the radio can be heard, but it also has a LOUD hum that does not go away. What could this be? I got to looking at the wires around the radio and noticed a wire that had a round plastic object the size of maybe a quarter, and about 3/4 inch thick. It looked like it could have been attached to something, what could this be? Any ideas to anyone? Thanks for help, M Wade

If my memory is still intact this is the power supply for the speaker maganet. If I am incorrect someone let me know.

[DonaldSmith]

Thhe speaker connector is the round thing in the photo.

If your speaker is not connected, and the loud hum is coming from the radio itself, it sounds that's the vibrator doing its thing. It may be normal. Mine has a wide rubber band around the case.

If the loud hum is in the speaker, and the volume knob does not turn it down, then the filter capacitors are shot, like when I fried my new ones by connecting them wrong (negative goes to the chassis, even with a positive grounded car).

For my radio, I got the replacement capacitors in, and next I have to fiddle with the new tubes (After a long weekend with the assembled children and grandchildren about 300 miles from here. Gotta go, she's yeling at me).

I'll report on my progress when I get into it next week.

[maurice wade]

Thanks for your help, guys. Now all I have to do is find out where these filter capacitors are located, and what they look like. MWade

[DonaldSmith]

On my radio, when I took off the side cover with the wing nut, I could see the tubes. There was a metal can that looks like a tube. That's where the filter capacitors were hiding, three in one cover.

Now, taking off the other side cover, the one with the nut holding it on, I could see the wiring, capacitors, resisters, etc. The bottom side of the can had three lugs with wire leads connected to them.

Here's where the schematic and other diagrams I downloaded from nostalgiaair came in handy. They showed layout of the components. Each lug is from one of the filter capactors in the can. They were labeled 10A, 10B and 10C. I made a diagram of all the leads conected to each capacitor, and took pictures.

My new filter capacitors are separate, so I mounted them under the chassis with all the other capacitors. I had to triple-check the connnections to get them to the right capacitor.

I'm away this weekend, so I can't test my work further. Good luck to us both.

[MarcDeSoto]

Also when you have your radio man rebuild your radio, have him put in an RCA jack receptacle for your electronic devices such as your Ipod, Ipad, Iphone, CD player etc.  That way you are not limited to what's on AM all the time.  You can even get Internet radio and FM on your old radio if you subscribe to an online service.  Also to brush up your radio servicing skills, watch this Chrysler filmstrip from 1951:

 

https://www.youtube.com/watch?v=rjHNHzlHFjE

Edited January 17, 2015 by MarcDeSoto

[denmopar]

A few general tips:

 

 If you decide to refurbish your radio, there are some important items to be sure to do:

 

 ALWAYS replace the "buffer" condenser (modern wording = capacitor) This type is  NOT supplied by all the boutique radio specialty stores.

The buffer MUST be properly rated at its design voltage (typically 1600 volts D.C.) and is made to withstand the extremely large spikes that it must handle.

AND it MUST be of the same capacity- not just "close enough"- as the original design calls for- or trouble is surely ahead.

 

 ALL the old paper capacitors are likely to be bad (DC leakage) by now. As has been noted above, these are relatively cheap to replace.

If you're lucky enough to resurrect the vibrator by "zapping" it with 120 volts AC with a 40 watt bulb in series, you are all set for a while.

 If not, here is a supplier of solid state classic car radio vibrators:  http://www.radiosforoldcars.com/vibrators.htm

Buying a NOS  mechanical vibrator from other sources is not a guarantee it will work out of the box.....Years of laying on a shelf can just as well cloud the contact points even if never used.

 

Seldom that it is just a tube that is causing the radio not to play.....Not that it can't happen, but if the radio has been sitting unused for years,the tubes usually don't go bad just from that.

 

If you got the vibrator to function, replaced the buffer capacitor with proper value and voltage ratings, replaced all paper capacitors and electrolytic capacitors and the radio still doesn't make a sound, there is one easy test that will point to either the audio section or the radio frequency section:

 

 Turn the volume fully up...With a finger touching the metal shank of a screwdriver, place the tip on the CENTER terminal of the three in-line terminals on the volume control. (Not the terminals at the rear of the power switch...) .

 If the audio section is working, a loud HUM will be heard from the speaker. That would place the trouble in the "RF" section of the radio...From the antenna to that point at the volume control. This will eliminate a lot of searching.

 

Don't forget to "peak" the antenna trimmer after reinstalling back in your vehicle.

 

This isn't all there is to it, but it is a start....Good luck with yours!

 

Den- an old radio guy.

Edited January 19, 2015 by denmopar

[Ulu]

Glad I read this thread, as I'd never thought about the positive ground/electrolytic capacitor issue myself. I come from the vacuum tube days myself, and as a kid I'd pick up old TV's and fix them. This always meant a trip to Radio Shack to use the tube tester.

 

Last time I was there, the people working the store had all been born in the IC era & would have had no clue what a tube tester is.

[Niel Hoback]

There used to be a tube tester in the drugstore on the corner from our house in the 60's.  I found it in a resale shop in the 80's and bought it for just a few bucks.  It works perfectly!